The present invention relates to sound absorbing material, to a method of using sound absorbing material and to a method of making sound absorbing material.
In a known sound absorbing material relatively soft, low density particles are glued together with the glue filling the spaces between the particles. The particles are approximately 5 to 20 mm in diameter. However such material is only able to absorb a relatively small amount of high frequency sound and a significant amount of medium and low frequency sound is reflected or transmitted through the material rather than being absorbed.
It is an object of the present invention to attempt to improve the acoustic performance of consolidated particulate material and to overcome at least some of the above described or other disadvantages.
According to one aspect of the present invention sound absorbing material includes a plurality of pieces connected together, each piece including pores extending at least partially into the pieces, the material also including openings extending at least partially through the material between adjacent pieces.
The pieces may comprise foam such as polyurethane foam. The foam may be recycled. The foam may be a high density foam or medium density foam, for instance having a density of more than 25 or less than 150 or preferably in the region of 100 to 120 kg/m3, before the pieces are connected together.
The pieces may be connected together by adhesion, such as by a binder. The binder may comprise less than 50% or less than 40% or more than 10% or more than 20% or in the region of 35% of the mass of the material.
The material may have been compressed down during manufacture by more than 25% or less than 75% or preferably in the region of 50%.
The porosity of the material may be less than 80% or more than 20% or more than 40% or in the region of 65%.
The material may have an initial porosity, before compression of more than 80% or in the region of 95%.
The material prior to consolidation may have a flow resistivity of less than 300 or less than 150 or more than 20 or more than 40 or in the region of 80 kPascals×sec/m2.
The material may have a Youngs modulus of more than 105 or less than 109 or approximately 107 Pascals.
The material may have a density of less than 800 or less than 600 or more than 100 or more than 200 or in the region of 400 kg/m3.
The ratio of the space provided by the pores to the total space in the material may be more than 60 or more than 70 or more than 80 or in the region of 85%. The ratio of the space provided by the openings to the total space in the material may be less than 40 or less than 30 or less than 20 or in the region of 15%.
The mean cross-sectional area of the pores may be less than 1.6 mm2 or less than 0.25 mm2 or more than 0.003 mm2 or more than 0.012 mm2 or in the region of 0.05 mm2.
The mean cross-sectional area of the openings may be less than 2 mm2 or less than 1.5 mm2 or more than 0.05 mm2 or more than 0.1 mm2 or in the region of 1.2 mm2.
The material may comprise vehicle sound absorbing material or construction sound absorbing material.
The mean cross-sectional dimension of the pieces in the material may be less than 10 or more than 0.5 or in the region of 3 to 5 mm.
At least one of the pores may be connected to at least one of the openings and preferably several pores are connected with several openings.
The material may be arranged to absorb more than 70 or more than 80 or more than 90% of the sound at at least one frequency. That frequency may be greater than 500 or greater than 600 or less than 6000 or less than 4000 or in the region of 800 Hz. Alternatively or additionally, that frequency may be more than 1100 or more than 1200 or less than 1600 or less than 1500 or in the region of 1300 Hz. The material may be arranged to absorb more than 70 or more than 80 or more than 90% of the sound at at least two spaced frequencies. The material may be arranged to absorb more than 30 or more than 40 or in the region of 50% or more of the sound at frequencies between the two spaced frequencies.
The material may comprise board material which may be less than 50 or less than 40 or more than 5 or in the region of 10 mm thick. The board material may be self supporting. The board material may be flexible.
The present invention also includes a method of using sound absorbing material as herein referred to comprising attaching the sound absorbing material to a vehicle or attaching the sound absorbing material to a construction.
The present invention also includes a method of making sound absorbing material comprising connecting a plurality of pieces together with each piece including pores extending at least partially into the pieces and the pieces also including openings extending at least partially through the material between adjacent pieces.
The method may comprise adhering the pieces together.
The method may comprise compressing the pieces, for instance by more than 25% or less than 75% or in the region of 50%.
The present invention also includes a method of making sound absorbing material as herein referred to.
According to a further aspect of the present invention a method of absorbing sound comprises using sound absorbing material as herein referred to.
The method may comprise sound travelling along a pore and then an opening connected to that pore or, alternatively or additionally, along an opening and then along a pore connected to that opening.
The present invention includes any combination of the herein referred to features or limitations.